Engine Classification
Financial or legal field · Modification blocked by policy
Reason: Dates must be in YYYY-MM-DD (ISO 8601) format for KSeF. Automatic date format conversion is not safe due to ambiguity (e.g., 01/02/2024 could be January 2nd or February 1st). Configure your invoicing software to output dates in ISO 8601 format.
What is KSEF-007?
KSEF-007 is a fatal validation rule defined in the KSeF specification (POL national rules).
When this rule fires, the invoice is rejected by Peppol access points and never reaches the buyer.
Why This Error Matters
KSEF-007 is a hard failure — the invoice must be corrected and re-sent before it can reach the recipient.
Validator Behavior
- ·Causes invoice rejection
- ·Error returned: KSEF-007
- ·Specification: KSeF
How to Fix It
Technical Reference
Code Example
<DataWystawienia>2026-02-15</DataWystawienia>Common Causes
- ·Polish date format DD.MM.YYYY used
- ·Incorrect separator
- ·Software default format wrong
Seeing this in production? The API handles KSEF-007 automatically. See the fix response →
Frequently Asked Questions
All dates in KSeF invoices must be in YYYY-MM-DD (ISO 8601) format. Other formats are rejected.
Use ISO 8601 date format (YYYY-MM-DD). This error involves a protected field — Invoice Navigator flags it in your pipeline so your team can correct it at the source.
Yes, KSEF-007 is a critical error that will cause invoice rejection. It must be fixed before submission to ensure your invoice is accepted by the recipient's system.
KSEF-007 involves a financial or legal field that cannot be auto-modified by policy. Invoice Navigator detects and flags this error immediately, but the correction must be made manually in your ERP or invoicing software.
Related Content
Last updated: 3 March 2026
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This error involves a financial field that can't be auto-modified. We'll flag it with a clear diagnosis so you can fix it at the source.